La Defense is the business district of Paris, even if it is in fact located just outside of Paris.
La Defense is a grey and cold area : many high buidilngs for business and a huge shopping mall (the biggest of Europe), but nothing else : almost nobody live there.
Thus, it is still an interesting place, due the the Grande Arche and the straight axis from it to the Ar de Tromphe and even farther to the Louvre Palace Museum.

La Defense : esplanade

Grande Arche

Grande Arche

Grande Arche

La Defense

You can see the Arc de Triomphe (Triumph Arc) in the back.

La Defense

La Defense : Grande Arche

La Defense : esplanade

Mac Donald's at La Defense

Les Quatre Temps shopping mall

Inside the big shopping mall.

More about La Defense

La Défense is a major business district for the city of Paris (French:"Ville de Paris"), bordering Neuilly-sur-Seine, west of the city proper. It is centred on an ovular loop of roadway straddling the Hauts-de-Seine département municipalities of Nanterre, Courbevoie and Puteaux. The district is at the westernmost extremity of Paris' Historical Axis, which commences at the Louvre in the centre of Paris and crosses the Champs-Élysées and the Arc de Triomphe.
Around its Grande Arche and esplanade ("le Parvis") centre, this district holds many of the Paris urban area's tallest high-rises: with its 3.5 million m² of office space, La Défense is the largest business district in Europe.